High-Performance Nylon-6 Sustainable Filaments for Additive Manufacturing

Topology-Optimized Splints vs Casts for Distal Radius Fractures: A Randomized Clinical Trial

Importance

To date, there is currently no evidence-based medical support for the efficacy of topology-optimized splints in treating distal radius fractures.

Objective

To assess the clinical efficacy and complication rates of topology-optimized splints in the treatment of distal radius fractures after closed manual reduction.

Design, Setting, and Participants

This 12-week, multicenter, open-label, analyst-blinded randomized clinical trial (comprising a 6-week intervention followed by a 6-week observational phase) was carried out from December 3, 2021, to March 10, 2023, among 110 participants with distal radius fractures. Statistical analysis was performed on an intention-to-treat basis between June 3 and 30, 2023.

Intervention

Participants were randomly assigned to 2 groups: the intervention group received topology-optimized splint immobilization and the control group received cast immobilization after closed manual reduction for 6weeks. After this period, immobilization was removed, and wrist rehabilitation activities commenced.

Main Outcomes and Measures

The primary outcome was the Gartland-Werley (G-W) wrist score at 6 weeks (where higher scores indicate more severe wrist dysfunction). Secondary outcomes encompassed radiographic parameters, visual analog scale scores, swelling degree grade, complication rates, and 3 dimensions of G-W wrist scores.

Results

A total of 110 patients (mean [SD] age, 64.1 [12.7] years; 89 women [81%]) enrolled in the clinical trial, and complete outcome measurements were obtained for 101 patients (92%). Median G-W scores at 6 weeks were 15 (IQR, 13-18) for the splint group and 17 (IQR, 13-18) for the cast group (mean difference, -2.0 [95% CI, -3.4 to -0.6]; P = .03), indicating a statistically significant advantage for the splint group. At 12 weeks, no clinically significant differences in G-W scores between the 2 groups were observed. Complication rates, including shoulder-elbow pain and dysfunction and skin irritation, were less common in the splint group (shoulder-elbow pain and dysfunction: risk ratio, 0.28 [95% CI, 0.08-0.93]; P = .03; skin irritation: risk ratio, 0.30 [95% CI, 0.10-0.89]; P = .02).

Conclusions and Relevance

Findings of this randomized clinical trial suggest that patients with distal radius fractures that were managed with topology-optimized splints had better wrist functional outcomes and fewer complications at 6 weeks compared with those who received casting, with no difference at week 12. Therefore, topology-optimized splints with improved performance have the potential to be an advisable approach in the management of distal radius fractures.

Trial Registration

Chinese Clinical Trial Registry: ChiCTR2000036480.

Prototype Design for Grading Structures in Powder Bed Fusion Processes

While targeted alignment in certain additive manufacturing (AM) methods such as material extrusion (MEX) and stereolithography (SLA) has been well documented in the research community, a method for targeted alignment of added fillers or fibrous materials in powder bed fusion (PBF) AM devices has yet to be successfully achieved. Similarly, incorporation of multimaterials does not work easily with any of the AM technologies. This study creates a prototype design that could be integrated into a PBF system to allow for multimaterial layer deposition and alignment of powders and powder blends. The rheological properties of polyamide powder and a range of polyamide composite blends (incorporating milled carbon fibre, graphite flakes, polytetrafluoroethylene, and glass microspheres) in different concentrations were studied, and together with the particle size distribution and particle morphology analysis were applied for the design of a prototype hopper for incorporation in the PBF system to create targeted multimaterial deposition. Different concept designs, multichambered and multi-hopper with hopper angles calculated specifically for the composite blend powders selected, were proposed. Initial deposition trials outside a PBF process were tested, and the deposited layers were measured.

Nanomaterials Reinforced Polymer Filament for Fused Deposition Modeling: A State-of-the-Art Review

For the past years, fused deposition modeling (FDM) technology has received increased attention in the applications of industrial manufacturing fields, particularly for rapid prototyping, small batch production and highly customized products, owing to the merits of low-cost, user-friendliness and high design freedom. To further expand the application potential and promote the performance of the as-manufactured products, many efforts have been spent on the development of suitable materials for FDM applications. In recent years, the involvement of nanomaterials in the FDM-based polymer matrix, which has been demonstrated with great opportunities to enhance the performance and versatility of FDM printed objects, has attracted more and more research interest and the trend is expected to be more pronounced in the next few years. This paper attempts to provide a timely review regarding the current research advances in the use of nanomaterials to reinforce polymer filaments for the FDM technique. Polymer composite filaments based on nanomaterials such as carbon nanotubes, nanoclay, carbon fibers, graphene, metal nanoparticles and oxides are discussed in detail regarding their properties and applications. We also summarized the current research challenges and outlooked the future research trends in this field. This paper aims at providing a useful reference and guidance for skilled researchers and also beginners in related fields. Hopefully, more research advances can be stimulated in the coming years.

Influence of Antibacterial Coating and Mechanical and Chemical Treatment on the Surface Properties of PA12 Parts Manufactured with SLS and MJF Techniques in the Context of Medical Applications

Additive manufacturing (AM) is a rapidly growing branch of manufacturing techniques used, among others, in the medical industry. New machines and materials and additional processing methods are improved or developed. Due to the dynamic development of post-processing and its relative novelty, it has not yet been widely described in the literature. This study focuses on the surface topography (parameters Sa, Sz, Sdq, Sds, Str, Sdr) of biocompatible polyamide 12 (PA12) samples made by selective laser sintering (SLS) and multi jet fusion (MJF). The surfaces of the samples were modified by commercial methods: four types of smoothing treatments (two mechanical and two chemical), and two antibacterial coatings. The smoothing treatment decreased the values of all analyzed topography parameters. On average, the Sa of the SLS samples was 33% higher than that of the MJF samples. After mechanical treatment, Sa decreased by 42% and after chemical treatment by 80%. The reduction in Sdq and Sdr is reflected in a higher surface gloss. One antibacterial coating did not significantly modify the surface topography. The other coating had a smoothing effect on the surface. The results of the study can help in the development of manufacturing methodologies for parts made of PA12, e.g., in the medical industry.

Repurposing of waste PET by microbial biotransformation to functionalized materials for additive manufacturing

Plastic waste is an outstanding environmental thread. Poly(ethylene terephthalate) (PET) is one of the most abundantly produced single-use plastics worldwide, but its recycling rates are low. In parallel, additive manufacturing is a rapidly evolving technology with wide-ranging applications. Thus, there is a need for a broad spectrum of polymers to meet the demands of this growing industry and address post-use waste materials. This perspective article highlights the potential of designing microbial cell factories to upcycle PET into functionalized chemical building blocks for additive manufacturing. We present the leveraging of PET hydrolyzing enzymes and rewiring the bacterial C2 and aromatic catabolic pathways to obtain high-value chemicals and polymers. Since PET mechanical recycling back to original materials is cost-prohibitive, the biochemical technology is a viable alternative to upcycle PET into novel 3D printing materials, such as replacements for acrylonitrile butadiene styrene. The presented hybrid chemo-bio approaches potentially enable the manufacturing of environmentally friendly degradable or higher-value high-performance polymers and composites and their reuse for a circular economy.

ONE-SENTENCE SUMMARY

Biotransformation of waste PET to high-value platform chemicals for additive manufacturing.

Emerging plastic litter variants: A perspective on the latest global developments

Plastic litter is one of key reasons of environmental concern due to its adverse effect on ecosystem and health. Exposure of plastic litter to anthropogenic and ecological conditions results in a variety of emerging litter variants that fluctuate in composition, mechanical, and chemical properties. Considering the properties of these plastic litter variants, it is anticipated that the transportation of foreign species or microbial pathogens together with these litter variants is most likely to affect the marine ecosystem. Moreover the plastic litter may enter the plastic cycle or marine biota and can spread across the ocean. Very recently several emerging plastic litter variants such as anthropoquinas, plasticrust, pyroplastic, plastitar, and plastiglomerate have been reported along the coastal areas across the oceans. The purpose of this perspective is to comprehend these emerging plastic litter variants, integrate the latest developments and highlight their adverse effects on the coastal ecosystem. Further, it details the make-up, place of origin, and management strategies for these plastic litter variants.

Fused Deposition Modelling of Polymer Composite: A Progress

Additive manufacturing (AM) highlights developing complex and efficient parts for various uses. Fused deposition modelling (FDM) is the most frequent fabrication procedure used to make polymer products. Although it is widely used, due to its low characteristics, such as weak mechanical properties and poor surface, the types of polymer material that may be produced are limited, affecting the structural applications of FDM. Therefore, the FDM process utilises the polymer composition to produce a better physical product. The review's objective is to systematically document all critical information on FDMed-polymer composite processing, specifically for part fabrication. The review covers the published works on the FDMed-polymer composite from 2011 to 2021 based on our systematic literature review of more than 150 high-impact related research articles. The base and filler material used, and the process parameters including layer height, nozzle temperature, bed temperature, and screw type are also discussed in this review. FDM is utilised in various biomedical, automotive, and other manufacturing industries. This study is expected to be one of the essential pit-stops for future related works in the FDMed-polymeric composite study.

A Review of Polymer-Based Materials for Fused Filament Fabrication (FFF): Focus on Sustainability and Recycled Materials

Recently, Fused Filament Fabrication (FFF), one of the most encouraging additive manufacturing (AM) techniques, has fascinated great attention. Although FFF is growing into a manufacturing device with considerable technological and material innovations, there still is a challenge to convert FFF-printed prototypes into functional objects for industrial applications. Polymer components manufactured by FFF process possess, in fact, low and anisotropic mechanical properties, compared to the same parts, obtained by using traditional building methods. The poor mechanical properties of the FFF-printed objects could be attributed to the weak interlayer bond interface that develops during the layer deposition process and to the commercial thermoplastic materials used. In order to increase the final properties of the 3D printed models, several polymer-based composites and nanocomposites have been proposed for FFF process. However, even if the mechanical properties greatly increase, these materials are not all biodegradable. Consequently, their waste disposal represents an important issue that needs an urgent solution. Several scientific researchers have therefore moved towards the development of natural or recyclable materials for FFF techniques. This review details current progress on innovative green materials for FFF, referring to all kinds of possible industrial applications, and in particular to the field of Cultural Heritage.

Ocean plastics: environmental implications and potential routes for mitigation - a perspective

This review provides a current summary of the major sources and distribution of ocean plastic contamination, their potential environmental effects, and prospects towards the mitigation of plastic pollution. A characterization between micro and macro plastics has been established, along with a comprehensive discussion of the most common plastic waste sources that end up in aquatic environments within these categories. Distribution of these sources stems mainly from improper waste management, road runoff, and wastewater pathways, along with potential routes of prevention. The environmental impact of ocean plastics is not yet fully understood, and as such, current research on the potential adverse health effects and impact on marine habitats has been discussed. With increasing environmental damage and economic losses estimated at $US 1.5 trillion, the challenge of ocean plastics needs to be at the forefront of political and societal discussions. Efforts to increase the feasibility of collected ocean plastics through value-added commercial products and development of an international supply chain has been explored. An integrative, global approach towards addressing the growing ocean plastic problem has been presented.

Predictive Models for the Characterization of Internal Defects in Additive Materials from Active Thermography Sequences Supported by Machine Learning Methods

The present article addresses a generation of predictive models that assesses the thickness and length of internal defects in additive manufacturing materials. These modes use data from the application of active transient thermography numerical simulation. In this manner, the raised procedure is an ad-hoc hybrid method that integrates finite element simulation and machine learning models using different predictive feature sets and characteristics (i.e., regression, Gaussian regression, support vector machines, multilayer perceptron, and random forest). The performance results for each model were statistically analyzed, evaluated, and compared in terms of predictive performance, processing time, and outlier sensibility to facilitate the choice of a predictive method to obtain the thickness and length of an internal defect from thermographic monitoring. The best model to predictdefect thickness with six thermal features was interaction linear regression. To make predictive models for defect length and thickness, the best model was Gaussian process regression. However, models such as support vector machines also had significative advantages in terms of processing time and adequate performance for certain feature sets. In this way, the results showed that the predictive capability of some types of algorithms could allow for the detection and measurement of internal defects in materials produced by additive manufacturing using active thermography as a non-destructive test.

Sustainable Additive Manufacturing: Mechanical Response of Acrylonitrile-Butadiene-Styrene over Multiple Recycling Processes

Sustainability in additive manufacturing refers mainly to the recycling rate of polymers and composites used in fused filament fabrication (FFF), which nowadays are rapidly increasing in volume and value. Recycling of such materials is mostly a thermomechanical process that modifies their overall mechanical behavior. The present research work focuses on the acrylonitrile-butadiene-styrene (ABS) polymer, which is the second most popular material used in FFF-3D printing. In order to investigate the effect of the recycling courses on the mechanical response of the ABS polymer, an experimental simulation of the recycling process that isolates the thermomechanical treatment from other parameters (i.e., contamination, ageing, etc.) has been performed. To quantify the effect of repeated recycling processes on the mechanic response of the ABS polymer, a wide variety of mechanical tests were conducted on FFF-printed specimens. Regarding this, standard tensile, compression, flexion, impact and micro-hardness tests were performed per recycle repetition. The findings prove that the mechanical response of the recycled ABS polymer is generally improved over the recycling repetitions for a certain number of repetitions. An optimum overall mechanical behavior is found between the third and the fifth repetition, indicating a significant positive impact of the ABS polymer recycling, besides the environmental one.